Nanotechnology is viewed as a promising technology with the potential to produce a technology revolution in the twenty-first century. Among leading nanomaterials shouldering the advance of nanotechnology are fullerenes.
Fullerenes are carbonaceous materials in the form of hollow spherical cages typified by C60 (Buckminsterfullerene) and have attracted the interest of many scientists as a new research subject since their discovery by Smalley and Kroto in 1985. Attempts have been made to take advantage of the unique structure of fullerenes to develop novel functional materials with various practical applications.
For example, the superconductivity transition temperature of C60 crystal is 18K, whereas it was found that C60 HBr3, a derivative compound of C60, achieves a superconductivity transition temperature as high as 117K. As this temperature is much higher than the temperature of liquid nitrogen, it represents a major step forward in the elucidation of the mechanism by which superconductivity is introduced and the practical application of superconductive materials. In the field of alternative energy resources, the ability of fullerenes to absorb hydrogen is expected to lead to their use as hydrogen-storage materials in fuel cells and for other purposes. In the field of medicine and life science, fullerenes can be used as carriers for new pharmaceutical or efficacious components, because the fullerene molecule, called the Bucky ball, is characterized in being inactive and nontoxic, being so small as to easily interact with cells, proteins, viruses and the like, and being variously modifiable. Thus, fullerenes are being used to develop medicines for combating the AIDS virus, amytrophic lateral sclerosis, osteoporosis and other disorders. A wide range of applications are also being studied in the fields of electronic materials and composite materials. Not only are fullerenes finding applications such as those mentioned above but it has also been pointed out in the environmental field that fullerenes may be contained in exhaust gases. Thus, elucidation of the activity of these nanomolecules is also required from the viewpoint of learning how they influence the environment and the human body.
In contrast to conventionally known general molecules, fullerenes, typified by C60, and their derivatives are distinctive from the viewpoint of physical properties in that each molecule rotates as a whole, and it has already been demonstrated that the state or condition of such molecular motion strongly influences the functions exerted by the molecules (R. D. Johnson et al., “C60 Rotation in the Solid State-Dynamics of a Faceted Spherical Top” Science, 255, (6), 1235–1238 (1992)). For example, as the interactions among the molecules of fullerenes or their derivatives intensify, the molecular rotation speed (the number of rotations) thereof decreases.
Thus, in developing applications or uses of fullerenes or their derivatives in various fields as mentioned above, it is important to know the molecular rotation speed thereof since it serves as important information for evaluating the fullerenes or their derivatives. A method hitherto reported for measuring the molecular rotation speed of fullerenes or their derivatives utilizes a nuclear magnetic resonance (NMR) apparatus for the measurement (R. Tycko et al., “Molecular Dynamics and the Phase Transition in Solid C60” Phys. Rev. Letters, 67, (14), 1886–1889 (1991); R. Tycko et al., “Molecular Orientational Dynamics in Solid C70: Investigation by One and Two dimensional Magic Angle Spinning Nuclear Magnetic Resonance” J. Chem. Phys., 99, (19), 7554–7564 (1993)). This method requires an expensive apparatus and since the measurement is destructive, an “in situ” measurement is not possible. In addition, the method is not suitable for evaluating fullerenes in life science and the like since the measurement is carried out in vacuo.
The object of the present invention is to provide a novel method by which the molecular rotation speed of fullerenes or fullerene derivatives can be measured in a relatively simple and inexpensive manner.